The present invention relates to novel 4-(2-pyridyl)piperizines, to pharmaceutical compositions containing them and to their medicinal use. The compounds of the present invention are potent and selective partial agonists at serotonin 7 (5-HT7) receptors, and are capable of modulating circadian rhythms. They are useful in treating treatment of depression, anxiety, migraine, and eating disorders, as well as disorders or conditions the treatment which can be effected or facilitated by altering circadian rhythms. Examples of such disorders and conditions are seasonal affective disorder, bipolar disorder, jet lag, sleep disorders such as circadian sleep rhythms disorder, sleep deprivation, REM sleep disorders, hypersomnia, parasomnias, sleep-wake cycle disorders, narcolepsy, sleep disorders associated with blindness, sleep disorders associated with obesity, and sleep disorders associated with shift work or irregular work schedules; nocturnal enuresis, and restless legs syndrome.
Serotonin 7 receptors are present in the suprachiasmatic nucleus (SCN), the brain region that contains the biological clocks, and their activation leads to a resetting of the clocks as a function of dose and timing of treatment. Such a mechanistic link is evident in numerous paradigms—in in vitro electrophysiological studies of SCN neuronal activity, and in light induced changes in wheel running behavior and nighttime melatonin suppression—in each case activation of 5HT7 receptors having the potential to modulate both clock function and the clock resetting ability of light. Full agonists and partial agonists of the 5HT7 receptor therefore offer a wide range of clinically useful therapeutics.
The present invention also relates to a method of treating depression or anxiety in a mammal, including a human, by administering to the mammal a 5HT7 partial agonist in combination with an antidepressant or an anxiolytic agent. It also relates to pharmaceutical compositions containing a pharmaceutically acceptable carrier, a 5HT7 partial agonist and an anxiolytic agent or antidepressant.
The connection between the 5-HT7 receptor and CNS disease such as depression and circadian rhythm disorders has been disclosed in a number of publications, including Lopez-Rodriguez, et. al., Bioorg. Med. Chem. Lett., 10 (2000) 1097–1100.
Glennon's article “Serotonin Receptors: Clinical Implications”, Neurscience and Behavioral Reviews, 14, 35–47 (1990), refers to the pharmacological effects associated with serotonin receptors including appetite suppression, thermoregulation, cardiovascular/hypotensive effects, sleep, psychosis, anxiety, depression, nausea, emesis, Alzheimer's disease, Parkinson's disease and Huntington's disease.
Serotonin 7 partial agonists are useful for the treatment of depression. As used herein, the term “depression” includes depressive disorders, for example, single episodic or recurrent major depressive disorders, and dysthymic disorders, depressive neurosis, and neurotic depression; melancholic depression including anorexia, weight loss, insomnia and early morning waking, and psychomotor retardation; a typical depression (or reactive depression) including increased appetite, hypersomnia, psychomotor agitation or irritability, anxiety and phobias, seasonal affective disorder, or bipolar disorders or manic depression, for example, bipolar I disorder, bipolar II disorder and cyclothymic disorder.
Other mood disorders encompassed within the term “depression” include dysthymic disorder with early or late onset and with or without a typical features; dementia of the Alzheimer's type, with early or late onset, with depressed mood; vascular dementia with depressed mood, disorders induced by alcohol, amphetamines, cocaine, hallucinogens, inhalants, opioids, phencyclidine, sedatives, hypnotics, anxiolytics and other substances; schizoaffective disorder of the depressed type; and adjustment disorder with depressed mood.
Encompassed within the term “depression” are: depression in cancer patients, depression in Parkinson's patients, postmyocardial infarction depression, subsyndromal symptomatic depression, depression in infertile women, pediatric depression, major depression, single episode depression, recurrent depression, child abuse induced depression, and post partum depression.
Major depression is characterized by feelings of intense sadness and despair, mental slowing and loss of concentration, pessimistic worry, agitation, and self-deprecation. Physical changes also occur, especially in severe or “melancholic” depression. These include insomnia or hypersomnia, anorexia and weight loss (or sometimes overeating), decreased energy and libido, and disruption of normal circadian rhythms of activity, body temperature, and many endocrine functions.
Treatment regimens for depression commonly include the use of tricyclic antidepressants, monoamine oxidase inhibitors, some psychotropic drugs, lithium carbonate, and electroconvulsive therapy (ECT) (see R. J. Baldessarini in Goodman & Gilman's The Pharmacological Basis of Therapeutics, 9th Edition, Chapter 19, McGraw-Hill, 1996 for a review). More recently, new classes of antidepressant drugs are being developed including selective serotonin reuptake inhibitors (SSRIs), specific monoamine reuptake inhibitors and 5-HTIA receptor agonists, antagonists and partial agonists.
Serotonin 7 partial agonists are also useful for the treatment of anxiety. As used herein, the term “anxiety” includes anxiety disorders, such as panic disorder with or without agoraphobia, agoraphobia without history of panic disorder, specific phobias, for example, specific animal phobias, social phobias, obsessive-compulsive disorder, stress disorders including post-traumatic stress disorder and acute stress disorder, and generalized anxiety disorders.
“Generalized anxiety” is typically defined as an extended period (e.g., at least six months) of excessive anxiety or worry with symptoms on most days of that period. The anxiety and worry is difficult to control and may be accompanied by restlessness, being easily fatigued, difficulty concentrating, irritability, muscle tension, and disturbed sleep.
“Panic disorder” is defined as the presence of recurrent panic attacks followed by at least one month of persistent concern about having another panic attack. A “panic attack” is a discrete period in which there is a sudden onset of intense apprehension, fearfulness or terror. During a panic attack, the individual may experience a variety of symptoms including palpitations, sweating, trembling, shortness of breath, chest pain, nausea and dizziness. Panic disorder may occur with or without agoraphobia.
“Phobias” includes agoraphobia, specific phobias and social phobias. “Agoraphobia” is characterized by an anxiety about being in places or situations from which escape might be difficult or embarrassing or in which help may not be available in the event of a panic attack. Agoraphobia may occur without history of a panic attack. A “specific phobia” is characterized by clinically significant anxiety provoked by feared object or situation. Specific phobias include the following subtypes: animal type, cued by animals or insects; natural environment type, cued by objects in the natural environment, for example storms, heights or water; blood-injection-injury type, cued by the sight of blood or an injury or by seeing or receiving an injection or other invasive medical procedure; situational type, cued by a specific situation such as public transportation, tunnels, bridges, elevators, flying, driving or enclosed spaces; and other type where fear is cued by other stimuli. Specific phobias may also be referred to as simple phobias. A “social phobia” is characterized by clinically significant anxiety provoked by exposure to certain types of social or performance circumstances. Social phobia may also be referred to as social anxiety disorder.
Other anxiety disorders encompassed within the term “anxiety” include anxiety disorders induced by alcohol, amphetamines, caffeine, cannabis, cocaine, hallucinogens, inhalants, phencychdine, sedatives, hypnotics, anxiolytics and other substances, and adjustment disorders with anxiety or with mixed anxiety and depression.
Anxiety may be present with or without other disorders such as depression in mixed anxiety and depressive disorders. The compositions of the present invention are therefore useful in the treatment of anxiety with or without accompanying depression.
Anxiety disorders are generally treated using benzodiazepine sedative-antianxiety agents. Potent benzodiazepines are effective in panic disorder as well as in generalized anxiety disorder, however, the risks associated with drug dependency may limit their long-term use. 5-HTIA receptor partial agonists also have useful anxiolytic and other psychotropic activity, and less likelihood of sedation and dependence (see R. J. Baldessarini in Goodman & Gilman's Tite Pharmacological Basis of Therapeutics, 9th Edition, Chapter 18, McGraw-Hill, 1996 for a review).